CN103666523B - Work starting method for catalytic cracking unit - Google Patents

Abstract

The invention relates to a work starting method for a catalytic cracking unit. The method comprises the steps of infusing a hot fluidizing medium to a regenerator and a reactor, so as to heat the regenerator and the reactor, shutting off valves between the regenerator and the reactor, and loading a fresh catalyst into the regenerator; when the regenerator reaches a certain temperature, infusing burning oil which contains metal salts of organic acids to the regenerator; infusing water vapor to an external circulation pipe, so as to increase the pressure of the regenerator; after the activity of the catalyst in the regenerator is lowered by 10-50%, stopping infusing the burning oil and the water vapor, recovering the pressure of the regenerator, and conveying the catalyst to the reactor; enabling the catalyst in the reactor to enter a precipitator for gas-solid separation, and returning the separated catalyst to the regenerator; spraying a hydrocarbon oil raw material into the reactor for catalytic cracking reaction. According to the method, the activity of the fresh catalyst can be rapidly lowered to an equilibrium catalyst level before oil spraying by making full use of the existing devices and conditions, so that the catalyst replacement link in the conventional methods is avoided, and the unit is put into normal operation in shorter time.

Description

A method for starting a catalytic cracking unit

technical field

The invention relates to a method for starting a catalytic cracking unit, more specifically, a method for starting a reactor and a regenerator system of an industrial catalytic cracking unit using fresh catalyst.

Background technique

Fluid catalytic cracking (FCC) is the most important heavy oil lightening process in the current oil refining industry. With the gradual increase in the demand for light petroleum products, new catalytic cracking units have been continuously put into operation around the world.

The start-up process of the reactor and regenerator system of the catalytic cracking industrial unit generally follows the following basic steps: firstly, the air is heated in the auxiliary combustion chamber by burning combustible gas and/or liquid, and then injected into the regenerator and the reactor in sequence, so that the temperature of the two devices is raised to 350°C-550°C; then close the valve on the catalyst circulation pipeline between the two devices, and continue to inject hot air into the regenerator, and feed water vapor into the reactor; then inject the catalyst into the regenerator and make the catalyst under the action of hot air Perform single-device fluidization in the regenerator; spray combustion oil into the regenerator at a suitable temperature, so that the catalyst in the regenerator continues to heat up to about 600°C; wait for the catalyst in the regenerator to be fluidized normally and establish a suitable catalyst material Slowly open the valve on the regenerated catalyst delivery pipeline between the regenerator and the reactor, and transfer part of the high-temperature catalyst in the regenerator to the reactor in a fluidized state; A certain amount of catalyst is used to maintain the catalyst level in the regenerator; after the catalyst in the reactor has a certain reserve and is fluidized normally under the action of water vapor, slowly open the catalyst delivery pipeline between the reactor and the regenerator. The valve allows the catalyst in the reactor to return to the regenerator in a fluidized state, and establishes a two-stage circulating fluidization of the catalyst between the regenerator and the reactor; when the temperature, pressure and catalyst storage of the two devices reach the set value Finally, inject hydrocarbon oil feedstock into the reactor for catalytic cracking reaction and obtain products, and complete the start-up process of the catalytic cracking industrial device reactor and regenerator system.

Catalysts used in the start-up process of catalytic cracking industrial units are generally industrial balance catalysts from similar units, and a few units are started with specially developed low-activity start-up catalysts. The reason why fresh catalysts are not used during the start-up process is mainly because the activity of fresh catalysts is very high, and the reaction of hydrocarbon oil raw materials on fresh catalysts will produce a large amount of coke, resulting in a large amount of coke "piling up" on the catalyst, which in turn leads to not working. In most cases, even similar catalytic cracking units have different feedstock properties and product requirements, so the catalysts used in normal operation are not exactly the same. In order to achieve the expected product distribution, no matter which of the above start-up schemes is adopted, the catalyst used in the start-up process must be slowly replaced with a fresh catalyst specially designed for the unit after the unit is running stably.

Compared with the start-up process of using other equipment balance catalysts and low-activity start-up special catalysts, the direct use of fresh running catalysts can avoid the catalyst replacement link, so that the unit can be put into normal operation in a shorter time, thereby saving the refinery during the start-up process. However, the problem that needs to be solved is how to quickly reduce the activity of the fresh catalyst to the level of the equilibrium catalyst before fuel injection.

It is a very mature method to reduce the activity of catalysts by hydrothermal treatment in the laboratory. The research results show that under the normal operating pressure of the catalytic cracking unit, it is usually necessary to treat the fresh catalytic cracking catalyst with 100% steam at a high temperature of 730°C-830°C to obtain a catalyst with an activity similar to that of the equilibrium catalyst. In the start-up stage, the reaction regeneration system of the catalytic cracking industrial unit relies on the heating method of fuel injection to provide the heat required by the system. Due to the limitation of the device material and the temperature tolerance of the catalyst, the temperature of the two units is generally controlled below 700 °C. It can be seen that the catalytic cracking unit cannot reach the temperature conditions required for laboratory hydrothermal treatment during the start-up stage.

CN1124899C discloses a method for circularly polluting and aging catalytic cracking catalysts, which is to inject the hydrocarbon oil raw material dissolved in metal organic compounds into the reactor to contact and react with the regeneration agent, and to separate the oil gas and catalyst after the reaction, and the oil gas is sent to the subsequent separation System, after the reacted catalyst is stripped, aged by steam and flue gas, and regenerated by oxygen-containing gas, it is transported to the reactor for recycling. After the fresh catalyst is treated by this method, its physical and chemical properties are close to the industrial equilibrium catalyst. This method is implemented on small and medium-scale experimental devices, and is not suitable for catalytic cracking industrial devices.

CN101927198A and CN101927199A disclose a treatment method for improving the selectivity of catalytic cracking catalysts. Fresh catalysts are loaded into a dense-phase fluidized bed, contacted with water vapor, and aged in a certain hydrothermal environment to obtain aged catalysts. The aged catalyst is fed into an industrial catalytic cracking unit. This method can make the activity and selectivity distribution of the catalyst in the catalytic cracking unit more uniform, and its implementation requires the operating catalytic cracking unit to provide necessary external conditions, and the catalytic cracking unit in the start-up stage cannot adopt this method.

Contents of the invention

The purpose of the present invention is to propose a method for starting a catalytic cracking unit using a fresh catalyst on the basis of the existing catalytic cracking industrial unit start-up method.

The start-up method of catalytic cracking unit provided by the invention comprises the following steps:

(1) After injecting the hot gas-phase fluidized medium into the regenerator and reactor of the catalytic cracking unit to heat up, close the valves on the regenerated catalyst delivery pipeline between the regenerator and the reactor and on the waiting catalyst delivery pipeline, and continue to the regenerator Put hot gas-phase fluidized medium into the reactor, and put fresh catalyst into the regenerator, so that the catalyst is in a fluidized state in the regenerator, wherein the regenerator is equipped with a catalyst external circulation pipe;

(2) When the internal temperature of the regenerator rises above 350°C, inject combustion oil that can spontaneously ignite at this temperature and contain metal organic acid salts into the regenerator to contact and burn with fresh catalyst;

(3) Open the valve on the external circulation pipe of the catalyst, inject water vapor into the external circulation pipe through the loose air inlet of the external circulation pipe to contact with the fresh catalyst, and increase the pressure of the regenerator, and use water vapor in the external circulation pipe under pressurized conditions. The fresh catalyst in the fluidized state is processed in the circulation pipe;

(4) When the micro-reaction activity of the catalyst in the regenerator drops by 10%-50%, change the water vapor injected into the external circulation pipe into loose wind, and after the pressure of the regenerator is reduced to a normal level, open the regenerated catalyst delivery pipeline. The valve is used to transport the catalyst with reduced micro-reaction activity to the reactor through the regenerated catalyst delivery pipeline;

(5) The catalyst in the reactor enters the settler for gas-solid separation under the impetus of another gas-phase fluidized medium, and the separated catalyst enters the waiting catalyst delivery pipeline;

(6) Open the valve on the delivery pipeline of the raw catalyst to return the catalyst to the regenerator, and establish the circulating fluidization of the catalyst between the regenerator and the reactor;

(7) Spray hydrocarbon oil raw materials into the reactor to carry out catalytic cracking reaction and obtain reaction products.

Method provided by the invention is implemented like this:

The hot gas-phase fluidized medium is injected into the bottom of the regenerator of the catalytic cracking unit, and introduced into the reactor through the regenerated catalyst delivery pipeline and the spent catalyst delivery pipeline between the regenerator and the reactor. The regenerator is equipped with a catalyst external circulation pipe. The fluidizing medium in step (1) is selected from one or more of air, oxygen, combustible gas combusted in air or oxygen, and combustible liquid combusted in air or oxygen.

After the internal temperature of the regenerator and reactor reaches at least 300°C, close the valves on the regenerated catalyst delivery pipeline and the spent catalyst delivery pipeline. The hot gas-phase fluidizing medium continues to be injected into the regenerator, and another gas-phase fluidizing medium is injected at the bottom of the reactor. The fluidized medium in the reactor can be the same as the fluidized medium in the regenerator in step (1), or steam, preferably steam.

The fresh catalyst is loaded into the regenerator, so that the catalyst is in a fluidized state under the action of the fluidized medium. The catalyst is any catalyst suitable for use in a catalytic cracking unit.

When the internal temperature of the regenerator reaches above 350°C, combustion oil that can spontaneously ignite at this temperature and contain one or more metal organic acid salts can be injected into the regenerator to contact and burn with fresh catalyst. The metal is selected from one or more of iron, nickel, vanadium, calcium, sodium, and magnesium, and the organic acid is selected from carboxylic acids, hydroxy acids, keto acids, sulfonic acids, sulfinic acids, and thiocarboxylic acids. One or more, wherein the carboxylic acid is selected from one or more of naphthenic acid, fatty acid and aromatic acid, preferably naphthenic acid. The combustion oil is selected from one or more of the diesel fractions obtained by various processing means, including one or more of straight-run diesel oil, catalytic cracking diesel oil, coked diesel oil, F-T synthetic diesel oil, and hydrogenated diesel oil. kind.

Open the valve on the outer circulation pipe, and inject water vapor into the outer circulation pipe through the loose air inlet of the outer circulation pipe to contact with the fresh catalyst. The superficial linear velocity of water vapor in the external circulation pipe is controlled to be 0.1 m/s-0.7 m/s, preferably 0.1 m/s-0.5 m/s.

Increase the pressure of the regenerator, and treat the fresh catalyst in a fluidized state at a pressure of 0.3MPa-3.0MPa, preferably 0.3MPa-1.0MPa, and a temperature of 550°C-700°C, preferably 600°C-680°C. The steam is superheated under the pressure of the regenerator. The pressures mentioned in the present invention all refer to absolute pressures.

When the micro-reaction activity of the catalyst in the regenerator drops by 10%-50%, preferably 15%-30%, stop injecting combustion oil containing metal-organic substances, change the water vapor injected into the external circulation pipe into loose wind, and turn the regenerator The pressure drops to a normal level (generally lower than 0.3MPa), and then the valve on the regenerated catalyst delivery pipeline is opened, and part of the catalyst with reduced activity is delivered to the reactor through the regenerated catalyst delivery pipeline. Described catalyst activity adopts ASTM D3907 or its improved method to measure.

The catalyst in the reactor is driven by the gas phase fluidization medium into the settler for gas-solid separation, and the separated catalyst enters the raw catalyst delivery pipeline. Open the valve on the spent catalyst delivery line to return the catalyst to the regenerator, and establish the circulating fluidization of the catalyst between the regenerator and the reactor. Afterwards, the hydrocarbon oil raw material is injected into the reactor to carry out the catalytic cracking reaction and the reaction product is obtained, and the start-up process of the catalytic cracking unit is completed.

The method provided by the invention is suitable for all fluidized reactors, fluidized regenerators and catalytic cracking catalysts. Wherein the fluidized reactor includes but not limited to various forms of risers, various forms of fluidized beds, various forms of delivery lines or a combination thereof, the structure of the fluidized regenerator and the quantity are not limited, and the composition of the catalytic cracking catalyst is not limited.

The beneficial effects of the method provided by the invention are:

The method provided by the invention makes full use of the conditions that can be provided in the start-up stage of the catalytic cracking unit itself, and can be implemented without modifying the interior of the unit, so the normal operation of the catalytic cracking unit will not be affected.

The method provided by the invention can quickly reduce the activity of the fresh catalyst to the level of the equilibrium catalyst before fuel injection, thereby avoiding the catalyst replacement link after the conventional start-up method, and putting the device into normal operation in a shorter time, Thereby saving the cost input of the refinery during the start-up process.

Description of drawings

Fig. 1 is a schematic flow chart of a method for starting a catalytic cracking unit using fresh catalyst provided by the present invention, and the regenerator of the catalytic cracking unit shown in Fig. 1 is provided with a catalyst external circulation pipe.

Detailed ways

The method provided by the present invention will be described in detail below in conjunction with the accompanying drawings, but the present invention is not limited thereto.

As shown in Figure 1, the hot gas-phase fluidized medium containing oxygen is injected into the bottom of the regenerator 10 of the catalytic cracking unit through the pipeline 1, and passes through the regenerated catalyst delivery pipeline 2 and the spent catalyst delivery pipeline between the regenerator 10 and the reactor 6 8 is introduced into reactor 6 and settler 7. After the internal temperature of the regenerator 10, the reactor 6 and the settler 7 reaches at least 300° C., the valves 3 and 9 on the regenerated catalyst delivery pipeline 2 and the spent catalyst delivery pipeline 8 are closed. The hot gas-phase fluidized medium containing oxygen continues to be injected into the regenerator 10 through the pipeline 1, and another gas-phase fluidized medium is injected into the bottom pipeline 4 of the reactor 6. The fresh catalyst is loaded into the regenerator 10, so that the catalyst is in a fluidized state under the action of the fluidized medium containing oxygen. When the internal temperature of the regenerator 10 reaches above 350°C, the combustion oil which can spontaneously ignite at this temperature and contains one or more metal-organic substances is sprayed into the regenerator 10 from the pipeline 16 to contact with the fresh catalyst and burn. Open the valve 14 on the outer circulation pipe 13, inject water vapor into the outer circulation pipe 13 through the loose air inlet 15 of the outer circulation pipe 13 to contact with the fresh catalyst, and control the apparent linear velocity of the water vapor in the outer circulation pipe 13 to be 0.1 m /sec ~ 0.7 m/sec. Increase the pressure of the regenerator 10 to 0.3MPa~1.0MPa through the regulating valve 12 on the flue gas pipeline 11, and use water vapor to treat the fresh catalyst in the fluidized state in the external circulation pipe 13 at a temperature of 550°C~700°C . The steam is superheated under the pressure of the regenerator 10 . When the microreaction activity of the catalyst in the regenerator 10 drops by 10% to 50%, stop injecting combustion oil and water vapor containing metal-organic substances, and reduce the pressure of the regenerator 10 to a normal level through the regulating valve 12 on the flue gas pipeline 11 , and then open the valve 3 on the regenerated catalyst delivery line 2, and transport the partially deactivated catalyst to the reactor 6 through the regenerated catalyst delivery line 2. The catalyst in the reactor 6 is driven by the gas-phase fluidized medium from the pipeline 4 into the settler 7 for gas-solid separation, and the separated catalyst enters the spent catalyst delivery pipeline 8 . The valve 9 on the spent catalyst delivery line 8 is opened to return the catalyst to the regenerator 10 , establishing a circulating fluidization of the catalyst between the regenerator 10 and the reactor 6 . Afterwards, the hydrocarbon oil raw material is injected into the reactor 6 from the pipeline 5 to carry out the catalytic cracking reaction and the reaction product is obtained, and the start-up process of the catalytic cracking unit is completed.

The method provided by the present invention is further illustrated below by way of examples, but the present invention is not thereby limited in any way.

The catalyst used in the examples is industrially produced by China Petroleum & Chemical Corporation Catalyst Qilu Branch, and the trade name is MMC-2. The catalyst contains ultra-stable Y-type zeolite and ZSP zeolite with an average pore diameter of less than 0.7 nanometers. The main physical and chemical properties of MMC-2 fresh catalyst are shown in Table 1. The metal organic acid salt used is a commercially available product, produced by U.S. Strem Chemicals. The microreaction activity of catalyst in the embodiment all adopts ASTM D3907 method to measure.

Example 1

Example 1 illustrates the effect of metal contamination and hydrothermal treatment of fresh catalysts using the method provided by the present invention.

A pressurized fixed fluidized bed experimental device was used to simulate the conditions in the start-up stage of the catalytic cracking unit regenerator. 100 grams of MMC-2 fresh catalyst was loaded into the fixed fluidized bed, and air was passed into the bottom of the fluidized bed as the fluidizing medium. The catalyst in the fixed fluidized bed is heated and stabilized at 660°C by means of electric heating, and the pressure of the fixed fluidized bed is controlled at 0.4MPa through the automatic pressure regulating valve at the outlet of the fixed fluidized bed. Then experiment with the following steps:

(1) Inject straight-run diesel oil dissolved in vanadium naphthenate with a vanadium content of 20ppm into the bottom of the fixed fluidized bed at a rate of 0.5kg/hour, and pollute the catalyst metal for 1 hour;

(2) Immediately vaporize and overheat water to 400°C and pass it into the bottom of the fluidized bed, and stop injecting straight-run diesel oil containing vanadium naphthenate and air into the fluidized bed to control the surface of water vapor in the fluidized bed The apparent linear velocity is 0.3 m/s, and the temperature and pressure of the fluidized bed are kept constant, and the catalyst is subjected to hydrothermal treatment for 1 hour;

(3) Pass air into the bottom of the fluidized bed as the fluidized medium, stop injecting the superheated steam in step (2) into the fluidized bed, keep the temperature and pressure of the fluidized bed constant, and repeat step (1);

(4) Repeat step (2) and step (3) alternately, and stop the test after repeating step (2) 23 times.

By the above-mentioned test method, 24 hours of metal pollution and 24 hours of hydrothermal treatment have been completed alternately for the fresh catalyst, which is used to simulate the fresh catalyst provided by the present invention to carry out metal pollution and water treatment respectively in the regenerator and the external heat collector at the same time. The method of heat treatment. The main conditions of the treatment and the microreaction activity of the catalyst after treatment are listed in Table 2.

Example 2

Example 2 illustrates the effect of using the method provided by the invention, using different metals and changing the treatment conditions to pollute and hydrothermally treat fresh catalysts.

The basic method of the experiment is the same as in Example 1, except that the metal organic acid salt in straight-run diesel oil is a mixture of iron naphthenate and sodium naphthenate, and the content of iron and sodium in straight-run diesel oil is 30ppm. The pressure of the fixed fluidized bed is controlled at 2.2 MPa, the temperature of the catalyst is controlled at 680° C., and the superficial linear velocity of water vapor in the fluidized bed is 0.6 m/s. The catalyst was hydrothermally treated under the above conditions for 6 hours. The main conditions of the treatment and the microreaction activity of the catalyst after treatment are listed in Table 2.

Comparative example 1

Comparative Example 1 illustrates the effect of hydrothermal treatment of only fresh catalyst under the same hydrothermal treatment conditions as in Example 1.

The basic method of the experiment is the same as in Example 1, and the main operating conditions and results are listed in Table 2.

Comparative example 2

Comparative Example 2 illustrates the effect of hydrothermally treating only fresh catalyst for a longer period of time under lower pressure conditions compared to Example 1.

The basic method and most of the hydrothermal treatment conditions of the experiment are the same as in Example 1, except that the pressure of the fixed fluidized bed is controlled at 0.2 MPa, and the treatment time is extended to 72 hours. The main operating conditions and results are listed in Table 2.

The experimental result of embodiment 1 and embodiment 2 in table 2 shows, adopt method provided by the invention, under the condition that fresh catalyst can provide under the start-up stage of catalytic cracking unit, only by 24 hours metal pollution and hydrothermal treatment just can The activity is reduced to the level of the equilibrium catalyst, indicating that the industrial catalytic cracking unit can be started with fresh catalyst by adopting the method provided by the invention. Comparing Example 1 with Comparative Example 1 and Comparative Example 2, it can be seen that under the same hydrothermal treatment conditions, the method provided by the invention can significantly accelerate the activity decay rate of the fresh catalyst; The activity of the fresh catalyst cannot be effectively reduced even if the treatment time is greatly extended.

Table 1

Catalyst MMC-2 Zeolite content, weight % Y 16 ZSP 12 physical properties Specific surface, ^m2 /g 258 Pore volume, ^cm3 /g 0.19 Apparent density, g/ ^cm3 0.75 Sieve, wt% 0-20 microns 0.8 0-40 microns 10.4 0-80 microns 70.8 0-110 microns 88.5 0-149 microns 97.8 >149 microns 2.2 microreactive activity 91

Table 2

Claims (12)

1. a catalytic cracking unit start-up method, is characterized in that the method comprises the following steps:

(1) after making it heat up the gas phase fluidization medium of heat injection For Fcc Regenerator and reactor, close the valve on regenerated catalyst line and reclaimable catalyst line of pipes between revivifier and reactor, continue the gas phase fluidization medium passing into heat in revivifier and reactor, and live catalyst is loaded in revivifier, make catalyzer be in fluidized state in revivifier, wherein revivifier is provided with external catalyst circulation pipe;

(2) when the internal temperature of revivifier is elevated to more than 350 DEG C, injecting in revivifier at such a temperature can spontaneous combustion burning containing the combustion oil of metal organic acid salt and contacts fresh catalyst, one or more in described metal chosen from Fe, nickel, vanadium, calcium, sodium, magnesium, described organic acid be selected from carboxylic acid, thionothiolic acid, alcohol acid, ketone acid, sulfonic acid,-sulfinic acid one or more;

(3) valve on external catalyst circulation pipe is opened, water vapor is injected in outer circulating tube and contacts fresh catalyst by the loosening wind entrance of outer circulating tube, and improve the pressure of revivifier, use water vapor in outer circulating tube, be in the live catalyst of fluidized state under pressure;

(4) after the micro-activity decline 10%-50% of revivifier inner catalyst, change the water vapor injecting outer circulating tube into loosening wind, after regenerator pressure is down to normal level, open the valve on regenerated catalyst line, the catalyzer after micro-activity being declined is delivered to reactor by regenerated catalyst line;

(5) catalyzer in reactor enters in settling vessel and carries out gas solid separation under the promotion of another strand of gas phase fluidization medium, and isolated catalyzer enters into reclaimable catalyst line of pipes;

(6) open the valve on reclaimable catalyst line of pipes, make catalyzer be back to revivifier, set up ciculation fluidized between revivifier and reactor of catalyzer;

(7) in reactor, spray into hydrocarbon oil crude material carry out catalytic cracking reaction and obtain reaction product.

2. method according to claim 1, is characterized in that step (2) described pressure is 0.3MPa-3.0MPa.

3. method according to claim 2, is characterized in that step (2) described pressure is 0.3MPa-1.0MPa.

4. method according to claim 1, is characterized in that the temperature of revivifier is 550 DEG C-700 DEG C.

5. method according to claim 4, is characterized in that the temperature of revivifier is 600 DEG C-680 DEG C.

6. method according to claim 1, is characterized in that one or more that described carboxylic acid is selected from naphthenic acid, lipid acid, aromatic acid.

7. method according to claim 1, is characterized in that the micro-activity decline 15%-30% of step (4) described catalyzer.

8. method according to claim 1, it is characterized in that step (1) described fluidizing medium be selected from air, oxygen, inflammable gas burn in air or oxygen after gas, flammable liquid burn in air or oxygen after gas among one or more.

9. method according to claim 1, is characterized in that described another strand of fluidizing medium of step (5) is identical with step (1) described fluidizing medium.

10. method according to claim 1, is characterized in that described another strand of fluidizing medium of step (5) is water vapor.

11. methods according to claim 1, is characterized in that the apparent linear velocity of water vapour in described outer circulating tube is 0.1 meter per second-0.7 meter per second.

12. methods according to claim 11, is characterized in that the apparent linear velocity of water vapour in described outer circulating tube is 0.3 meter per second-0.5 meter per second.